Enabler: add a new enabler to make file accesses more amenable for parallelization

[thhuang]

• Added a new enabler, noelle-io, to make file accesses more amenable for parallelization.
• Currently, the only transformation implemented in noelle-io is replacing all getc with getc_unlocked.
  • Since we will handle the synchronization manually, using the unlocked version of getc is safe without acquiring and releasing locks for files in runtime.
• The new enabler is tested on all test cases (https://github.com/arcana-lab/noelle/tree/master/tests) and benchmarks from https://github.com/arcana-lab/noelleGym.
• TODO: transformations that replace other stdio having an implicit locking mechanism.